High speed printing machines have been developed in recent years for printing data on computer paper, business forms and the like. The paper supplied to such printers is provided in webs of indeterminate length formed with longitudinally spaced, transversely oriented perforations. The paper is fed at high speeds from the web to the printer which prints the desired information on the individual sheets formed between adjacent perforations, and then discharges the printed sheets for further handling. In order to convert the continuous length of paper from the printer into a form which can be handled and shipped, the paper must be folded along its perforations as it is discharged from the printer.
One type of folding apparatus intended for use with high speed printers is a spiral zig-zag folder. Spiral zig-zag folders include a series of rollers which receive the paper from the printer and guide it to a reciprocating swing chute mechanism. The swing chute is driven forwardly and rearwardly relative to the frame of the folder through a distance or throw which is proportional to the distance between the longitudinally spaced transverse perforations in the paper. At both the forward and rearward limit of the throw of the swing chute, a set of beaters or knock-down fingers engages the paper in the area of its perforations and forces it into contact with one or more rotating spirals. The spirals resemble a screw having threads which are spaced progressively closer to one another from top to bottom. The paper is forced by the knock-down fingers into the top portion of the spirals, where the threads are spaced furthest apart, and as the spirals rotate the paper is transferred to progressively narrower threads thus forming a fold or crease along a perforation between adjacent, individual sheets of the paper. The sheets are then discharged from the spirals forming a zig-zag folded stack.
In addition to operating at high speeds, present day printers are also capable of accommodating different webs of paper each having a different spacing between the transverse perforations, or a different width. While the majority of business forms and computer paper are 81/2 inches in width, it is recognized that some forms must be narrower or wider depending upon the requirements of a particular customer. Additionally, it may be much more efficient to feed a web of wider paper through the printer, and then cut it in half or thirds prior to folding, instead of sending narrower webs of paper through the printer, one after the other, in order to obtain the desired quantity of business forms, computer sheets or the like.
Prior methods and apparatus of slitting and then stacking relatively wide webs of paper have a number of deficiencies. Such apparatus generally include a slitter mechanism located immediately downstream from the printer which forms one or more longitudinal slits extending partially through the paper web. The comparatively wide paper web is partially slit in half or in thirds, for example, thus forming two or more separable, longitudinally extending sections of paper. The partially slit paper web is then transferred to a folding apparatus of the type described above, e.g. including knock-down fingers and spirals, which zig-zag folds the paper into a single stack of individual sheets. Because the web of paper is only partially cut or slit longitudinally by the slitter, the operator must manually separate the single folded stack of individual sheets into two or more separate stacks, usually by moving his or her hand along each partially formed slit between the longitudinally extending sections of paper. This is not only a physically difficult hand operation which can injure the operator, but it also can produce ragged edges along the sides of each stacked section of paper where a slit is formed.
The reason prior art apparatus of the type described above do not completely cut or slit the wide paper web upstream from the folder is that difficulties have been encountered in handling, i.e. transferring and folding, two or more completely separated, relatively narrow sections of paper formed from the wider paper web. It has proven difficult to properly support and convey two or more separated sections of relatively narrow paper from the slitter to knock-down fingers and spirals, and such individual, narrow sections of paper tend to interfere with one another in the course of being folded. As a result, and as noted above, prior art methods and apparatus form only a partial slit in the wide web of paper so that the individual, longitudinally extending sections are not separated from one another in the course of being transferred from the slitter to the folding devices and/or during the folding operation itself. Although this facilitates the folding operation, the further step of separating the partially slit stacks from one another after folding remains a problem.